1. Field of the Invention
The present invention relates to a method and apparatus for melting materials containing fibers of inorganic material as well as organic substance and water, if any, in a furnace. The method according to the invention is particularly suitable for the melting of waste from production of mineral fibers, especially glass fibers, for which type of waste the percentage of fibers, organic substance and water can vary widely.
2. Discussion of the Background Art
One way of handling this type of waste from mineral fiber production is to dump it. For obvious reasons this is not a satisfactory method, particularly if the organic substance of the waste contains such substances as free phenol, formalin, oil or the like, which can cause environmental problems.
Melting is another method for the handling of this kind of fiber waste, which has been tested in many different ways, but without satisfactory results. Such a melting procedure is much more difficult to carry out in practice than might be imagined. When attempting to melt the waste by supplying external energy, a fairly solid melting mass is formed, which more or less stops the air supply to the organic substance of the waste. Furthermore, this melting mass has a doughy consistency, which is difficult to handle, especially if it sticks to the internal surfaces of the refuse incinerator. Also, waste fumes often contain unburnt gases, which cause air pollution. The problem cannot be solved in an economical way if the waste is exposed to very high temperatures in a conventional furnace, since it takes time before heat penetrates the material due to the low heat conductivity of the waste. The efficiency of such a construction is consequently very low.
Under these circumstances, experiments have been made to re-use the waste as raw material in glass furnaces, but this has proved to be possible only for waste having a small content of organic substance and with a very thorough decomposition of the fibrous waste, which also raises the price of the process considerably.
The melting method can be improved if the waste material is arranged on the surface of an existing melt in a special melting furnace, and melting heat is supplied by means of combustion heat from a number of burners arranged in the furnace, by means of current fed electrodes placed in the melt, or by means of current fed resistor elements built into the bottom of the furnace. A common problem for such methods, with which the waste is melted by heat from the environment, however, is that the energy consumption is high. Furthermore, it is still difficult to obtain waste fumes free from unburnt gases, and thus, the air pollution problem remains, at least partly.